The present invention relates to the field of receiving antennas, having a collapsible type of receiving stylus or stem or element, such as those used in many applications, for example for radio or TV sets, but particularly for use with radio sets on motor-vehicles.
As is well known, listening to a receiving radio set or receiver on a motor-vehicle involves the use of an efficient receiving antenna applied to the outside of the motor-vehicle.
At present, the most commonly used collapsible radio atennas are those of telescopically collapsible type of stylus, that is comprising a plurality of tubular sections of different diameter, so as to enter one another. Where electrical antennas are concerned, the various stylus sections are forced to move out in order to extend the antenna (or vice versa to re-enter for shortening thereof) by an inner nylon core which can be wound up or unwound from a drum, the latter being generally controlled by an electric motor. In some particular cases, band antennas of planar or slightly curved section have been also used, but such antennas have been scarcely used due to excessive flexibility in longitudinal directions.
It is the object of the present application to provide an antenna having a collapsible type of radio wave receiving element or stylus, the manufacture of which is by far less expensive than conventional antennas, while exhibiting all the advantages of the latter as to antenna operation and reception, and which is also sufficiently rigid to withstand normal operating conditions on a motor-vehicle.
Said objects have been accomplished by a type of antenna, wherein the stylus comprises a steel band or made of other material having characteristics of elasticity and flexibility, which band can be extended or retracted in a container body or housing, and taking at its extended or extracted portion a circular or ogive configuration in cross-section, or any configuration for assuring stability and strength thereof, while taking at its retracted portion a flattened straight configuration for winding up on a roller or drum.
Particularly, said band is during its preliminary manufacture stage shaped according to a curved shape along the longitudinal axis, thus causing it to have a tendency to take under normal conditions a tubular appearance with ogival, circular or other configuration in cross-section.
Such particular approximately tubular configurations taken by the subject band when being removed from its associated container body or housing enable the band to have an appropriate rigidity as to bending stresses exerted by wind or acceleration or deceleration movements or vibration of the motor-vehicle.
It is also an object of the present invention to provide an antenna of further improved type, comprising means for promoting a shape change in cross-section for the band forming the antenna stylus. The antenna also comprises means for limiting the friction between the body or housing and wound up stylus. Additionally, the improved antenna according to the present invention may be also made with a double band stylus in order to improve the strength thereof. Finally, the antenna band may be also preshaped according to a plurality of shapes.
Rather than in steel, an antenna band according to the invention can be made of other metals or alloys, or plastic materials or appropriate type of combined plastic materials and metals.
As above stated, the antenna according to the present invention is less expensive than conventional antennas, and at a same level of performances, it is less liable to jammings. The present antenna provides the additional advantages of a highly reduced maintenance, less possibilities of failures and improved electrical contact, since the stylus is an integral unit or element and the frictions increased by the sliding strain between the various tubes for antennas of telescopic type of stylus are removed.